Prevalence of Ultrasonographical Evidence of Gout in Psoriatic Arthritis “Psout”: Across-Sectional Study

Abstract

Background and Objectives: Psoriatic arthritis (PsA) and gout are conditions sharing several common risk factors. Serum uric acid levels are commonly raised in both, and it is observed that many patients presenting with gout have either clinical or family history of psoriasis. There are case report of overlapping PsA and gout called “Psout.” So the objective of this study was to find out ultrasonographic features of gout in patients with PsA. Methods: This was a prospective observational study conducted on 105 PsA patients. Serum uric acid and ultrasonography (USG) with color Doppler of the affected joint were performed to look for the presence of the double contour (DC) sign, snowstorm sign, and erosion that is specific for gout. The sensitivity of “tophus,” “snowstorm,” and the DC sign-on USG were 46%, 30.3%, and 60.1%, while the specificity was 94.9%, 90.9%, and 91.4%, respectively, for gouty arthritis. The sensitivity, specificity, positive predictive value, and negative predictive value of hyperuricemia (uric acid levels >6.8 mg/dL) were compared with USG findings in diagnosis of psout. Results: The prevalence of gout in PsA was 11.4% (12/105); 10/12, 2/12, 6/12, and 1/12 had DC sign, tophi, erosions, and snowstorm appearance, respectively. The sensitivity, specificity, positive predictive value, and negative predictive value of hyperuricemia in diagnosis of gout in PsA was 33.3%, 86%, 23.5%, and 90.9%, respectively. Conclusion: Psoriasis and gout can co-exist or mimic each other. Good presence of DC sign-on USG is a noninvasive method to diagnose gout in PsA patients. Those patients not responding to treatment for PsA may have co-existing gout, so we recommend USG in all patients with PsA, especially if they are not responding to treatment.